1. Field of the Invention
The present invention relates generally to semiconductor manufacture and, more particularly, to the packaging of a multiple semiconductor die assembly.
2. Description of Prior Art
Portable electronic devices such as, for example, radiotelephones, pagers and personal electronic assistants (PDAs), are becoming increasingly complex, while also being provided in increasingly smaller and lighter form factors. Semiconductor chips or dice such as, for example a microprocessor die and a memory die, are used within the portable electronic devices. Typically, a die is provided in a ceramic or plastic packaging that provides support, protection, dissipates heat for the die and provides a lead system for power and signal distribution.
There is a desire in the semiconductor packaging industry to minimize the profile (thickness) of semiconductor packages to facilitate advances in mobile, wireless, and medical applications. Current demands are for packages having profiles in the sub-millimeter level. A need for increased processing power and speed has also created a demand to increase the number of dies that can be fit into a given area (i.e., to increase die density) and to decrease the length of the electrical path between dies.
One solution to the demand for increased die density and decreased path length is known as a multi-chip module (CM), in which a number of dies are stacked inside a single molded package. Within the package, the dies are separated by insulating layers/interposers with wire-bond and/or flip die connections used to electrically connect the dies to a common lead frame. This solution, however, has its drawbacks. For example, a package with stacked dies introduces complexity in the assembly of the package due at least in part to the increased number of electrical connections and the need for an insulative layer/interposer to be disposed between the dies. If any defects occur during the assembly of the package, the entire package, including both chips, is unsalvageable.
One example of an MCM package is U.S. Pat. No. 6,452,278, issued Sep. 17, 2002, to Vincent DiCaprio et al. DiCaprio et al. describe a package including a substrate having a central aperture. DiCaprio et al. further describe one or more semiconductor dice disposed within the aperture to provide a thin profile.
As is appreciated by those in the art, there are higher costs associated with reworking a failure in packages including multiple dies as opposed to reworking a failed, single die package. To minimize rework cost, semiconductor manufacturing employs a Known Good Die (KGD) rule. Generally speaking, the KGD rule refers to a die level product provided by a semiconductor die manufacturer that carries with it a certain level of guaranteed reliability and, as a result, a higher price per die. The rule of thumb in MCM manufacturing is that if more than five dice of any given type, or devices with more than 200 bonds, are included in a single package, they should be KGD. This rule evolved from industry's experience with the high cost of rework at the die level compared to the cost of replacing failed, packaged parts at the board level. Cost impacts are likewise more severe when the user encounters a failed MCM, as opposed to the cost of replacing an individually packaged integrated circuit (IC).
Accordingly, the inventors realized that a need exists for semiconductor packages having higher die densities (e.g., more than one die in a package), a thin profile and which balance rework costs with the cost of procuring guaranteed KGD.